This invention relates to an apparatus and method for preparing a bone product. Specifically, the present invention relates to an apparatus and method for removing cancellous bone matrix, bone marrow and soft tissue from a bone portion.
Materials derived from bone, i.e., bone derivatives, such as bone powder, demineralized bone, biologically active proteins and collagens are used in a variety of applications, for example, replacing or repairing bone; covering or filling bone defects; as an osteogenic agent; and making photographic films, medical devices and bone meal. Bone derivatives are isolated or prepared from a cleaned bone product.
Generally, a bone product is made by removing undesired materials such as cancellous bone matrix, bone marrow and/or soft tissue from a bone. For example, in bone grafting, bone marrow is removed prior to being grafted on to a recipient to reduce the incidence of immune response. In a process for using a bone product as an osteogenic agent, the preparation of a bone product can involve physically cleaning the surface of a bone to remove periosteum and other soft tissues by scraping or brushing. The bone is then crushed into small fragments and washed with water to remove any water soluble materials remaining on the fragments. The fragments are then dried and extracted with lipophilic solvents, such as ethanol and ethyl acetate, to remove lipids. The fragments are then demineralized with acid and sterilized by irradiation, chemical sterilization, or other known solid sterilization techniques. This method of bone product preparation is time consuming and requires the use of organic solvents to remove remnants of soft tissues and other lipophilic compounds.
Another method for preparing a bone product is by comminuting a bone to a desired size and removing the soft tissues, such as meat and fat, that are present on the bone by a process such as a froth flotation process. For example, bone particles containing soft tissue are placed in a water bath and the air bubbles are introduced along with other chemicals to separate and remove soft tissue from bone fragments. One of the drawbacks of this process is that it requires time-consuming effort to remove undesired material from the bone particles. Another disadvantage of this process is that comminuting the bone lyses bacteria that are present on the bone thus releasing endotoxins and possibly contaminating bone particles with endotoxins.
Another drawback to this method is the use of organic solvents to remove lipids which may require expensive waste disposal. Moreover, this method requires comminuting unnecessary bone materials, which must be removed at a later stage of bone product preparation. Hence, a large amount of waste undergoes the same processing as the desired material, which can increase the overall cost.
U.S. Pat. No. 5,333,626 issued to Morse et al. (xe2x80x9cthe ""626 patentxe2x80x9d) discloses a method for preparing a bone product for a transplantation. The method involves cleaning a bone with a detergent at a high-pressure and elevated temperature to remove bone marrow while retaining the cancellous bone matrix. The ""626 patent requires primary decontamination of bone in order to remove bacteria and/or fungi which may be present on the bone. The bone is then cleaned using the high-pressure detergent without removing cancellous bone matrix. The method also requires repeated washing with sterile water to remove any detergent residue that may be left behind during the cleansing process.
Therefore, there is a need for preparing a bone product which removes a substantial portion of the undesired materials prior to comminuting the bone portion. There is also a need for reducing endotoxin contamination of a bone product during a comminuting process. In addition, there is a need for a simple and fast method for removing soft tissues without using an organic solvent or a froth flotation process.
The present invention includes a method for preparing a bone product which includes contacting an interior section of a bone portion with a first fluid medium to remove at least a portion of cancellous bone matrix from the bone portion. In one aspect, the pressure of the first fluid medium is at least about 3000 psi. The first fluid medium is preferably water. The method preferably includes removal of substantially all cancellous bone from the bone portion. The method can also include contacting an exterior section of the bone portion with a second fluid medium to remove at least a portion of soft tissue from the bone portion. By practice of the method, the resulting bone product can have a minimal amount of endotoxin, preferably less than about 300 xcexcg/g of the bone product, more preferably less than about 100 xcexcg/g of the bone product, more preferably less than about 50 xcexcg/g of the bone product, more preferably less than about 10 xcexcg/g of the bone product, and even more preferably less than about 1 xcexcg/g of the bone product.
A further embodiment of the present invention is an apparatus for preparing a bone product from a cylindrical bone portion. The apparatus includes a first interior nozzle for discharge of a pressurized fluid medium toward an interior surface of the bone portion and a retainer for retaining the bone portion so that an interior surface of the bone portion is exposed to the pressurized fluid medium. The apparatus also includes a fluid medium supply to supply fluid medium to the first interior nozzle at a pressure sufficient to remove at least a portion of cancellous bone matrix from the bone portion. In one embodiment of the apparatus, the pressurized fluid medium is discharged at a pressure of at least about 3000 psi. The apparatus can also include a second interior nozzle for discharge of a pressurized fluid medium toward an interior surface of the bone portion where the second interior nozzle is in opposing relation to the first interior nozzle. In a further embodiment, the retainer is made up of the first and second interior nozzles positioned to engage the interior circumference of first and second open ends, respectively, of the cylindrical bone portion.
The apparatus can also include a third exterior nozzle for contacting an exterior surface of the bone portion with a pressurized fluid medium. In this embodiment, the third exterior nozzle can direct the pressurized fluid medium toward the bone portion at an angle of incidence non-perpendicular to a tangent of the bone portion.
The apparatus can also include multiple sets of first, second and third nozzles arrayed in a circular configuration on a base. In this embodiment, the base can be indexed to rotate each of the sets of nozzles to a bone portion engagement station and to a bone product discharge station.
A further embodiment of the present invention is a method for producing a biologically active protein which includes removing soft tissue, marrow and cancellous bone matrix from a bone portion with a pressurized fluid medium to produce a bone product. This method further includes recovering a biologically active protein from the bone product. This method can also include demineralizing and/or comminuting the bone product before the step of recovering a biologically active protein.
A further embodiment of the present invention is a bone product comprising less than about 25% by weight cancellous bone matrix. Such a bone product can also have less than about 300 xcexcg of endotoxin per gram of the bone product. Such a bone product can also have less than about 25% by weight marrow.